OR I could say that the body as a whole works as a singular frame (this perspective is also a valid viewpoint) and the actual jin is a vector resultant that starts somewere below the dantien.
Mike Sigman

My impression based on my own sensation: any force (like the resultant force from the combination of several forces) has a single magnitude and direction, thus is said to be linear. However, to continually manifest a coherent, controllable resultant force from the whole body's (and partners') contributions, one should pay attention to the curves of the body's articulation.